Airborne mechanical pressure sensing and communication system



DAVID s. LITTLE B FREDERICK c. MELCHIOR A7 TORNEYS 3, 1963 E. w. PIKEETAL AIRBORNE MECHANICAL PRESSURE SENSI AND COMMUNICATION SYSTEM FiledMay 16, 1960 MM m N w mo m magma w 22223: I\ w 9% 8 WEEK 3 Qu H 3 Hmmmouzm 1 #565 W G IE I; R 8 R Q a.

llnited States Patent 0 AIREEGRNE R EE'CHANECAL PRESSURE ENSENG ANDCOMMUNICATZON SYSTEM Edward W. Ellie, 7 St. Nicholas Drive, Shepperton,England; David Little, 35 Eogart Ave, Port Washington, N.Y.; andFrederick C. Melchior, 258 Riverside Drive, New York, NX.

Filed May 16, 1?:50, Ser. No. 29,386

3 Claims. (Cl. 73-386) This invention relates to air to groundcommunications and, more particularly, to an airborne mechanicalpressure sensing system and associated communication system to transmitthe pressure measurement to a ground system.

In recent years, increased air traffic and the necessity of maintainingsafe separation of air trafiic during all weather operations hasresulted in development of systems for air trafiic control. In theUnited States, air traffic control is generally broken down into (a) Airroute trafi'ic control: covering en route trahic in designatedcontrolled airspace between airports, ([2) Approach and departurecontrol: handling IFR arrivals into and departures from airports, and(c) Airport traffic control: handling trafic in the immediate vicinityof and on an airport.

Since the objectives of air traidc control is to provide safe andexpeditious movement of air traffic, including the necessary control ofaircraft separation, the control function must obtain information as tothe position, speed, and flight path. In general, the information hasbeen supplied by the aircraft pilot in the form of position reports atspecific points. Unfortunately, the present air trafiic density is nowsuch as to overburden the slow, cumbersome method of voice reporting ofposition and confirming of ATC clearances.

In addition, the trafi'lc density and the increasing variation betweenspeeds of the individual aircraft in the control networks has made itclear that the present position reporting will not provide adequateinformation for proposed air traffic control. it is clear that moreinformation, rendered at more frequent intervals, is necessary to allowair traffic control systems to extrapolate from the position reports forflight path planning and control. Ground based computors can easilyhandle the necessary information storage and data processing. However,the data acceptance speed of computers and the increased informationnecessary for utilization of computer processing capabilities obsoletescumbersome voice communication.

It is planned to establish ground stations provided with the necessarycomputers. Upon interrogation, each aircraft will report positioninformation to the ground station. Such systems have been generallytermed data link systems.

In the data link systems proposed to date, each aircraft will beassigned an airframe address. The ground station Will reach the aircraftby interrogation, using the assigned address. The position informationof each aircraft will be communicated to the ground automatically inresponse to the interrogation signal. In this manner, the positioninformation may be requested by ground control at time intervals whichcan be adjusted to the traiiic and the reporting frequency needed forair traflic control. Digital coding of the information transmission andaddress information allows use of pulse train transmimion.

Of the many factors related to aircraft flight which bear on air trafiiccontrol, the factor of aircraft altitude, of direct concern to airt-rafiic control in the vertical plane, is that to Which thisapplication is directed.

' disclosed in Melchior Patent 2,760,260

3ft field Patented Dec. 3,, 1953 The art has proposed that aircraftaltitude be determined by slant-range, height-finding radar. Despiteintensive development, such altitude determination has not beensatisfactory.

Although aneroid sensors have the operational capabilities and theaccuracy necessary to determine aircraft altitude Within the accuracyrequired, the use of aneroid sensors has not been extensive due to thedifliculty of deriving vertical position information therefrom in formcompatible with the communication link and without loading the sensorwith a mechanical and/ or frictional load which would obviate theinherent accuracy of the sensor.

Although it is necessary to convert the pressure sensor (such as ananeroid capsule) measurement into altitude units for the display in theaircraft to have significance to the pilot, such conversion is notnecessary for transmission to a central co-mputor. The computer caneasily make this conversion, if necessary, or operate in pressure unitsif the flight path information (erg. obstacles) is stored in pressureunits. Thus a reduction in the complexity, Weight and size of theairborne unit is possible.

It is therefore the one object of this invention to provide an improvedmethod and means for determining the position of a mechanical sensor atselected intervals.

It is a further object of this invention to provide an improved methodand means for determining the position of a factor-responsive sensor andtranslating the position determination into a digitally coded signal.

Other objects and advantages of this invention will be pointed outhereinafter.

In accordance with these objects, there is provided, in a preferredembodiment of this invention, a pressure-responsive sensor comprisingstacked aneroid capsules. The capsules Will expand and contract inaccordance with chan es in ambient barometric pressure.

When the position of the capsule stack is to be determined (as forexample, on interrogation of the aircraft by a ground station), thecapsule stack is clamped in posi tion to prevent change of positionduring the positiondetermining cycle. A feeler is advanced into contactwith the capsule stack from a reference position, stopping when contactis made. Means responsive to the movement of the feeler are provided toset up in digitally coded form a signal directly related to capsuleposition. The signal is stored for read-out when the positioninformation is required.

To prevent displace .ent of the aneroid stack by the impinging feeler,means are provided to damp the feeler velocity when in incipientengagement with the capsule. Compensation means are provided to correctfor nonlinearity of the capsule stack deflection over the operatingrange to ensure accurate measurement of the ambient pressure and thusthe aircraft altitude.

The invention may be more clearly understood by reference to thefollowing description, taken in combina tion with the accompanyingdrawing, of which:

FIGURE 1 is a schematic diagram of a preferred embodiment of the presentinvention, and

FIGURE 2 is a side elevation of the portion of the apparatus shown inFIGURE 1.

Referring to the figures, there is shown a pressure-responsive sensorconsisting of stacked aneroid capsules 10 joined at their central hubs.Each of the capsules is preferably of the concentrically corrugateddiaphragm type One end of the stack is affixed to a structural member12. Carried by the other end of the capsule stack is a plunger 14.Movement of the plunger Will be the summation of the deflections of thediaphragms of the capsules due to the series coupling of the capsulesand is, thus, greater and more easily detected than the deflection ofany one capsule diaphragm. Additionally, stacking of the 3 capsulespermits selective matching of the deflection characteristics of eachcapsule, to improve the linearity of deflection of the capsule stackover the entire operating range.

The sensor stack will move the plunger in accordance with changes inambient barometric pressure over the entire operating range of thesensors. However, for this application, determination of sensor positionis required only in response to an interrogation signal from the groundcontroller. The interrogation signal is received by conventionalreceivers which are responsive only to properly addressed messages andused to operate switch 16 for readout of vertical position information.

To avoid error in position reporting by movement of the sensor duringthe read-out cycle, the sensor must be locked in position. For thispurpose there is provided a locking solenoid 22 which is energized frombattery 18 when switch 16 is closed by the interrogation signal. Whenthe solenoid is energized, the spring 24 coupled between the solenoidarmature 2s and a fixed support 28 will be overcome and the armature 26will move to clamp the plunger between the armature anvil 30 and thefixed anvil 32.

Thus, upon receipt of an interrogation signal, the sensor is clamped inposition to permit accurate reading of the position thereof and toprevent change in the position during the read-out cycle. In order todetermine the position of the plunger 14, there is provided a'mechanicalfeeler comprising rod 34, carrying a gauge face 36 at the end thereof.The feeler gauge is biased into a retracted position by a spring 38coupled between the eye 40 on the end of the rod and member 42. With theclosure of switch 16, however, solenoid 44 is energized and pulls inarmature 46. The movement of armature 46 will urge the feeler intocontact with the plunger 14 through spring 48 which has a spring contactsufiicient to overcome spring 38. Axial positioning of the feeler ismaintained by linear bearings 59, 52.

In order to translate linear movement of the feeler rod into a digitallycoded signal, there is provided a worm gear thread 54 extending alongthe feeler rod surface, which gear engages the matching threads onpinion 56 fixedly mounted on shaft 58. The profile and pitch of theteeth of gears 54 and 56 are selected to provide'nonlocking engagementtherebetween. Shaft 58 is rotatably mounted and is biased by ananti-back lash spring 66. Rotation of shaft 34 about its axis due totorque imposed by coaction of the worm gears 54, 56 is prevented by pin61 held against a stop 63 by spring 65.

Shaft 53 is operatively coupled to encoder 62, which sets up a digitallycoded signal linearly related to the shaft angular rotation. The digitalencoder may be any of the conventional encoders in which angularrotation sets up a digitally coded signal (as for example, a rotatabledisc carrying digitally coded angular position information read bydirect contact means, magnetic pickup, or optical scanning). Theencoderthen stores the digitally coded signal until it is required forcombination with other position information and transmission to theground station. The read-out and combining circuitry is known to theart.

Despite high clamping pressures obtainable by solenoid clamping of theplunger, the impact of rod 34 thereon may jolt the plunger from itsfrictionally held position. in order to damp the rod movement withoutadversely can affecting the traversal speed, there is provided a dampingdisc 64 coupled to shaft 58. An eddy current brake 65, is provided, thecoils of which are energized by source 18 when the circuit is completedby contact of the face plate 36 mounted on and insulated from rod 34- byinsulator block 37 with the defiectable spring contact 68 on theplunger. The circuit to ground is completed through the capsules in? andplunger 14. The action of the eddy current brake softens the impactwithout unnecessary loss of time in operation.

Although the capsules in the capsule stack may be matched for linearityof response, it is rarely possible to obtain absolute linearity over theentire operating range. To compensate for nonlinearity, the stop 63 isprovided with a cam surface 70 (FIGURE 2), which is custom calibratedfor the specific capsule stack used. The cam surface will, throughcoaction with pin 61, rotate the shaft 34- and output shaft 58 tocompensate for nonlinearity of capsule deflection.

The information as to vertical position may be extracted from thestorage element 62 by timer and transmission device 72. As soon as thesignal is transmitted to the ground station, the timer 72 resets switch16. On resetting of switch 16, the solenoids 22 and 44 are deenergized,allowing the apparatus to be reset by return of the feeler to thereference position via spring 38 and freeing of the sensor by return ofthe clamp 26 via spring 24.

This invention may be variously modified and embodied within the scopeof the subjoined claims.

What is claimed is:

1. An airborne mechanical pressure measuring system comprising aneroidcapsules arranged in a stack, one end of said stack being fixedlysecured, a plunger aifixed to the other end of said stack and movedthereby in accordance with changes in the pressure measured by saidaneroid capsules, a first solenoid means responsive to an electricsignal for clamping said plunger, a feeler rod,a second solenoid meansresponsive to said electric signal to drive said feeler rod from areference position into engagement with said plunger, said feeler rodbeing provided with threads along the length thereof, a rotatablymounted shaft having a pinion thereon, said pinion being provided withexternal threads which engage the threads on said feeler rod, thethreads on said pinion and said rod engaging in non-locking engagementto rotate said shaft as said feeler rod is advanced into contact withsaid plunger, and means to encode rotation of said shaft in digital formas a measure of said feeler movement from said reference position toprovide a measure of said pressure.

2. A system in accordance with claim 1 which includes means for slowingthe movement of said feeler when said feeler is in incipient contactwith said plunger.

3. A system in accordance with claim 2, which includes an eddy currentbrake energized when said feeler is in incipient engagement with saidplunger.

References Cited in the file of this patent UNITED STATES PATENTS1,332,182 Leeds Feb. 24, 1920 2,109,776 Johnson Mar. 1, 1938 2,364,450Keeler Dec. 5, 1944 2,729,780 Miller et aL Jan. 3, 1 956

1. AN AIRBORNE MECHANICAL PRESSURE MEASURING SYSTEM COMPRISING ANEROIDCAPSULES ARRANGED IN A STACK, ONE END OF SAID STACK BEING FIXEDLYSECURED, A PLUNGER AFFIXED TO THE OTHER END OF SAID STACK AND MOVEDTHEREBY IN ACCORDANCE WITH CHANGES IN THE PRESSURE MEASURED BY SAIDANEROID CAPSULES, A FIRST SOLENOID MEANS RESPONSIVE TO AN ELECTRICSIGNAL FOR CLAMPING SAID PLUNGER, A FEELER ROD, A SECOND SOLENOID MEANSRESPONSIVE TO SAID ELECTRIC SIGNAL TO DRIVE SAID FEELER ROD FROM AREFERENCE POSITION INTO ENGAGEMENT WITH SAID PLUNGER, SAID FEELER RODBEING PROVIDED WITH THREADS ALONG THE LENGTH THEREOF, A ROTATABLYMOUNTED SHAFT HAVING A PINION THEREON, SAID PINION BEING PROVIDED WITHEXTERNAL THREADS WHICH ENGAGE THE THREADS ON SAID FEELER ROD, THETHREADS ON SAID PINION AND SAID ROD ENGAGING IN NON-LOCKING ENGAGEMENTTO ROTATE SAID SHAFT AS SAID FEELER ROD IS ADVANCED INTO CONTACT WITHSAID PLUNGER, AND MEANS TO ENCODE ROTATION OF SAID SHAFT IN DIGITAL FORMAS A MEASURE OF SAID FEELER MOVEMENT FROM SAID REFERENCE POSITION TOPROVIDE A MEASURE OF SAID PRESSURE.